Sure, you can probably clone it - I’m not 100% sure, but I think laws protect that as long as it’s private use.
You can also fork it on GitHub, that’s something you agree to in the GitHub ToS - though I think you’re not allowed to push any modifications if the license doesn’t allow it?
Straight up taking the content from GitHub, uploading it to your own servers, and letting people grab a copy from there? That’s redistribution, and is something that needs to be permitted by the license. It doesn’t matter if it’s git or something else, in the end that’s just a way to host potentially copyrighted material.
Though if you have some reference on why this is not the case, I’d love to see it - but I’m not gonna take a claim that “that’s very much a part of most git flows”.
GPL is virally open source, because code using it needs to also be open source.
According to your comment, that doesn’t apply to BSD, so BSD isn’t virally open source, and the claim is true.
The reason some consider this better is because a company can’t fork the code, keeping it private, improving their version with paid workforce while also merging in changes to the original project, thus ending up with a superior version that they can then sell for profit, to no benefit of the opensource version or the people contributing to it.
There’s more reasons, and a whole ideological side, but I think that’s the main practical reason for using copyleft licenses, and a big one.